1. Field of the Invention:
This invention relates to a high-concentration pearling agent dispersion, and, more particularly, to a high-concentration pearling agent dispersion prepared by mixing a large amount of a fatty acid glycolic ester with specific types of solvent, heating the mixture, and then cooling it to deposit crystals of the fatty acid glycolic ester. The pearling agent dispersion comprises uniformly shaped crystals, has a low viscosity, and exhibits a superior stability at high and low temperatures.
2. Description of the Background:
Pearl-like gloss is often given to such compositions as shampoos, rinses, hair-washing creams, and liquid detergents in order to enhance their commercial value. One of the conventional methods of providing pearl-like gloss to such a composition is to mix it with a pulverized natural substance or an inorganic compound such as mica, fish scale, bismuth oxychloride, or the like. Another method is to crystallize a polyvalent metal salt of a higher fatty acid or a fatty acid glycolic ester.
Among these the method using a fatty acid glycolic ester is generally accepted in recent years. In this method a fatty acid glycolic ester which is solid at room temperature is added to a composition such as shampoo or the like, followed by heating of the mixture to melt the fatty acid glycolic ester, and then by cooling to recrystallize it, thereby providing pearl-like gloss to the composition. Alternatively, a pearling agent dispersion, e.g. a fatty acid glycolic ester dispersion, which is dissolved and cooled to recrystallize in advance, is mixed with a shampoo or the like at room temperature (Japanese Pat. Publication No. 804/1972, Japanese Pat. Application Laid-open Nos. 71021/1981, 216728/1983, etc.).
The method proposed by Japanese Pat. Publication No. 804/1972 is to employ a fatty acid glycolic ester together with a fatty acid dialkanol amide to induce pearl-like gloss. According to this method, however, if the pearling agent component is used at a high concentration the mixture becomes unreasonably viscous so that difficulty is encountered in handling it in the course of preparing a shampoo composition or the like at room temperature. In addition, it takes a long period of time to mix it homogeneously with other components.
Japanese Pat. Application Laid-open No. 71021/1981 discloses a method for preparing a pearling agent containing a fatty acid glycolic ester at a high concentration. This method, however, only provides a pearling agent with fatty acid glycolic ester crystals having varied crystal sizes and non-uniform crystal shapes. Thus, according to this method it is very difficult to produce a pearling agent providing a beautiful outward appearance.
Japanese Pat. Application Laid-open No. 216728/1983 discloses a pearling agent containing a salt of alkyl sulfate or a salt of polyoxyalkylene alkyl sulfate, a fatty acid dialkanol amide and water, as solvents, and a fatty acid glycolic ester at a high concentration. Alkyl sulfates contained in this pearling agent, however, have the drawback of producing a strong irritation to the skin. Use of an alkylether sulfate instead of an alkyl sulfate reduces irritation to the skin. In their manufacturing processes alkylether sulfates, however, are inevitably contaminated by dioxane, which is a potentially hazardous material.
In view of this situation, the present inventors have undertaken extensive studies for developing a high concentration pearling agent which is free from these drawbacks existing in the conventional pearling agents. As a result, the inventors have found that the use of an alkylsulfosuccinate or a polyoxyalkylenealkylsulfosuccinate, a fatty acid dialkanol amide, and water, together as solvents, mixed at a certain proportion with a fatty acid glycolic ester provides a high concentration, low viscosity pearling agent, which is less of an irritant, has crystals of a uniform shape, is stable at high and low temperatures, and provides a beautiful outward appearance. This finding has led to the completion of this invention.